1. Field of the Invention
The present invention generally relates to the field of lighting and in particular to methods and systems for controlling reflected light in lighting applications.
2. Related Arts
Lighting in a space is determined not just by the type and location of light sources contributing to the lighting of the space but also by the filtering and reflective properties of various media impacted by the light that reaches the space. Filtering occurs at translucent or partially translucent material in the path of the light. Reflection occurs at surfaces of objects receiving the light. Color, brightness, angle and other reflective properties of the materials reflecting the light affect the characteristics of the reflected light. Reflected light may provide a large part of lighting in a space.
Illumination occurs in two ways: direct and indirect. Direct light travels toward the subject from the illumination source. Direct light is generally controlled by the type of the light source, for example incandescent versus fluorescent, by the media placed directly between the source and the subject, for example louvers or translucent diffusion media, and by electrical or electronic dimming. Indirect light is reflected off a surface toward which the direct light source is aimed and then brought back onto the subject by the reflective medium. Reflective range varies from highly reflective, mirror-like and focusable to highly diffused or “soft.” Translucent media range varies from nearly clear to nearly opaque. Both types of diffusive media can be colored, as described below. Lighting fixtures utilize both direct and indirect light for various reasons related to the quality of light emitted by the specific component of the illumination process. Photographers, architects, and lighting fixture designers carefully choose the properties of lighting fixture's reflective surfaces to achieve the lighting effects they desire.
Both direct and indirect, or “bounce”, sources are used to create professional lighting effects. Various colored media may be used to act as the reflective surface for the lighting source. Examples of the colored media that are used to act as the reflective surface include foam core and heavy paper art board. Primarily white, black and to a much lesser extent, silver and gold are used as the color of the colored media.
Performance of the lighting fixture and functionality of a light-enhanced application are affected by reflected light. Variable intensity reflectors are not common. A limited number of lighting fixtures use mechanically variable reflectors. Such mechanical reflectors include a cylinder that is painted half in white and half in black. When the white half is showing, substantially all incident light is reflected. When the black half is showing all incident light is absorbed. The cylinder is rotated to expose a certain proportion of white depending on the degree of reflectivity that is desired.
In professional lighting,: only the Panavision Company's “PanaLite Eye Light” fixture is known to use a variable tone reflector to control light output. The device reflects light off a series of parallel rollers that are painted half white, half black and rotated to control output. For other reflected lighting applications, bouncing the light off of a reflective surface provides the most common solution.
Color temperature is a characteristic of visible light that has important applications in photography, videography, publishing and other related fields. Chromaticity is the quality of a color as determined by its purity and hue. The color temperature of a light source is determined by comparing its chromaticity with a theoretical, heated black-body radiator. The Kelvin temperature at which the heated black-body radiator matches the color of the light source is that source's color temperature.
Film stocks and video cameras are manufactured to reproduce white with respect to certain color temperatures. For example, 3200 deg Kelvin incandescent and 5800 deg Kelvin for “daylight” are two normal settings. As a result, consistent and controllable source color temperature is key to creating appropriate images. However, consistent control can be difficult to obtain because, for example, 1) incandescent sources, if dimmed electrically, change color throughout the dimming range; 2) fluorescent fixtures are largely undimmable and have widely varying color temperatures that change over the life of the globe; and 3) household and existing sources contain widely different lamp sources.
Gaining improved control over lighting provided by a light fixture or lighting provided to a space from natural light has presented these and other challenges to lighting experts.